Time-Dependent Effects of Haloperidol and Ziprasidone on Nerve Growth Factor, Cholinergic Neurons, and Spatial Learning in Rats

Transcription

1 /06/ THE JOURNAL OF PHARMACOLOGY AND EXPERIMENTAL THERAPEUTICS Vol. 318, No. 2 U.S. Government work not protected by U.S. copyright 99218/ JPET 318: , 2006 Printed in U.S.A. Time-Dependent Effects of Haloperidol and Ziprasidone on Nerve Growth Factor, Cholinergic Neurons, and Spatial Learning in Rats Alvin V. Terry, Jr., Vinay Parikh, Debra A. Gearhart, Anilkumar Pillai, Elizabeth Hohnadel, Samantha Warner, Henry A. Nasrallah, and Sahebarao P. Mahadik Departments of Pharmacology and Toxicology (A.V.T., D.A.G.) and Psychiatry and Health Behavior (A.P., S.P.M.) and Small Animal Behavior Core (A.V.T., E.H., S.W.), Medical College of Georgia, Augusta, Georgia; Department of Psychology, University of Michigan, Ann Arbor, Michigan (V.P.); Medical Research Service Line, Veterans Affairs Medical Center, Augusta, Georgia (A.P., S.P.M.); and Department of Psychiatry, University of Cincinnati, Cincinnati, Ohio (H.A.N.) Received November 29, 2005; accepted May 11, 2006 ABSTRACT In this rodent study, we evaluated the effects of different time periods (7, 14, 45, and 90 days) of oral treatment with haloperidol (HAL; 2.0 mg/kg/day) or ziprasidone (ZIP; 12.0 mg/kg/day) on nerve growth factor (NGF) and choline acetyltransferase (ChAT) levels in the hippocampus, and we subsequently assessed water maze task performance, prepulse inhibition (PPI) of the auditory gating response, and several NGF-related proteins and cholinergic markers after 90 days of treatment. Seven and 14 days of treatment with either HAL or ZIP resulted in a notable increase in NGF and ChAT immunoreactivity in the dentate gyrus (DG), CA1, and CA3 areas of the hippocampus. After 45 days, NGF and ChAT immunoreactivity had abated to control levels in ZIP-treated animals, but it was markedly reduced in HAL-treated subjects. After 90 days of treatment, NGF The newer pharmacological treatments for schizophrenia, now commonly referred to as second generation antipsychotics (SGAs), offer several advantages over first generation antipsychotics (FGAs) such as greater improvements in negative symptoms, prevention of relapse, increased functional capacity and quality of life, and fewer movement-related side effects (for review, see Miyamoto et al., 2005). It is also This study was supported in part by Pfizer, Inc., and by the National Institute of Mental Health Grant MH (to A.V.T.). Article, publication date, and citation information can be found at doi: /jpet and ChAT levels were substantially lower than controls in both antipsychotic groups. Furthermore, after 90 days of treatment and a drug-free washout period, water maze performance (but not PPI) was impaired in both antipsychotic groups, although the decrement was greater in the HAL group. Several NGFrelated and cholinergic proteins were diminished in the brains of subjects treated with either neuroleptic as well. These data support the premise that, although ZIP (given chronically) seems somewhat superior to HAL due to less pronounced behavioral effects and a more delayed appearance of neurochemical deficits, both antipsychotics produce time-dependent deleterious effects on NGF, cholinergic markers (i.e., important neurobiological substrates of memory), and cognitive function. generally believed that SGAs are superior to FGAs when their effects on cognition are considered (for reviews, see Keefe et al., 1999; Purdon, 1999), and some studies suggest that SGAs improve cognition in schizophrenia. This suggestion is of particular importance given that the degree of cognitive impairment in schizophrenia is recognized as an important predictor of social functioning, unemployment, and even relapse of psychiatric symptoms (for review, see Castner et al., 2004). It should be noted, however, that such conclusions regarding antipsychotics and cognitive function rely primarily on meta-analyses and short clinical trials (i.e., they rarely exceed a few months to 1 year in length). There- ABBREVIATIONS: SGA, second generation antipsychotic; FGA, first generation antipsychotic; HAL, haloperidol; ChAT, choline acetyltransferase; NGF, nerve growth factor; ZIP, ziprasidone; 5HT, 5-hydroxytryptamine; PBS, phosphate-buffered saline; DG, dentate gyrus; PBST, phosphate-buffered saline/tween 20; HRP, horseradish peroxidase; OD, optical density; AChEI, acetylcholinesterase inhibitor; mcpp, meta-chlorophenylpiperazine; PPI, prepulse inhibition; MK801, 5H-dibenzo[a,d]cyclohepten-5,10-imine (dizocilpine maleate); ELISA, enzyme-linked immunosorbent assay; VAChT, vesicular acetylcholine transporter; p75 NTR, p75 neurotrophin receptor; TrkA, tropomyosin receptor kinase A; P-TrkA, phosphotropomyosin receptor kinase A; SB, sample buffer; nachr, nicotinic acetylcholine receptor; machr, muscarinic acetylcholine receptor; BTX, -bungarotoxin; EPB, epibatidine; PRZ, pirenzepine; ANOVA, analysis of variance; DON, donepezil; SCOP, scopolamine; VEH, vehicle; AFDX 384, [ 3 H]-5,11-dihydro-11-[((2-(2-dipropylamino)- methyl)-1-piperidinyl)ethyl)amino)carbonyl]-6h-pyrido(2,3-b)(1,4)-benzodiazepin-6-one methanesulfonate. 709

2 710 Terry et al. fore, since schizophrenic patients are often treated with antipsychotics for decades, the aforementioned conclusions regarding SGAs may be premature. Since multiyear, prospective clinical studies designed specifically to identify neuroleptics that have optimal effects on cognition have not been conducted (and may be cost-prohibitive), animal studies designed to investigate such issues may be especially important. Furthermore, animal studies allow for rigorous investigations of the effects of chronic neuroleptic treatment on the neurobiological substrates of cognitive function. Previous work in our laboratories demonstrated that, in contrast to certain SGAs such as risperidone and clozapine, chronic oral haloperidol (HAL) treatment in rats resulted in sustained impairments in spatial learning performance as well as decrements in an important cholinergic marker, choline acetyltransferase (ChAT), in brain regions such as the cortex and hippocampus (Terry et al., 2002, 2003). This finding is potentially very important, because cholinergic activity in these brain areas is well documented to modulate a number of cognitive processes (for review, see Perry et al., 1999). Further work in our laboratories indicated that, although HAL treatment was associated with decrements in brain levels of the endogenous neurotrophin, nerve growth factor (NGF), and ChAT, this did not seem to be the case with the SGAs risperidone, clozapine, or olanzapine (Parikh et al., 2004a,b) at least up to a treatment period of 90 days. More recently, however, we detected decrements in NGF associated with HAL, risperidone, and olanzapine treatment for 180 days (Pillai et al., 2006), leading to the conclusions that such growth factor changes, although dependent on the length of treatment, may be common to several antipsychotics. Because the survival and function of adult mammalian cholinergic neurons (particularly those projecting from the basal forebrain to the cortex and hippocampus) are dependent on NGF (for review, see Counts and Mufson, 2005), we hypothesize that some of the unfavorable effects of HAL (and potentially other neuroleptics) on memory function may be related to time-dependent impairments in cholinergic activity due to reduced levels of NGF and/or its receptors. The novel SGA ziprasidone (ZIP) has a unique pharmacological profile with high affinity at a number of neurotransmitter receptors, including D 2, 5HT 1A, 5HT 2A, and 5HT 2C,as well as 5HT 1B/1D receptors (Seeger et al., 1995; Schmidt et al., 2001). It has proven efficacy in schizophrenia and related disorders (Goff et al., 1998; Daniel et al., 1999), as well as a low liability for certain adverse reactions, such as extrapyramidal symptoms and weight gain (for review, see Weiden et al., 2003). However, as in the cases highlighted above, the effects of long-term treatment with ZIP (particularly on cognitive function and neurobiological substrates of cognitive function) have not been evaluated. Therefore, the purpose of this study was to compare ZIP to the archetypal FGA HAL for effects on NGF and NGF receptors, key cholinergic proteins, and memory-related task performance in rats. The overall hypothesis was that chronic treatment with HAL or ZIP leads to sustained memory-related behavioral changes that are due (at least in part) to effects on NGF and/or its receptors and the regulation of key cholinergic marker proteins (i.e., for memory function). The two experimental approaches used to test this hypothesis were 1) to investigate a time course of exposure to either HAL or ZIP for effects on the cholinergic marker protein ChAT and the neurotrophin NGF and 2) to measure the effects of the neuroleptics on memoryrelated behavioral tasks, as well as the levels of NGF and cholinergic proteins after 90 days of treatment followed by a significant drug-free washout period. The latter experiments were designed to investigate the residual effects of prior chronic treatment with these agents (i.e., effects not associated with acute exposure). Materials and Methods Test Subjects Male albino Wistar rats (Harlan, Indianapolis, IN) (2 3 months old) were housed individually in a temperature-controlled room (25 C), maintained on a 12-h light/dark cycle with free access to food (Teklad Rodent Diet 8604 pellets; Harlan Teklad, Madison, WI). Water was allowed ad libitum for the first week in all test animals, but then it was replaced with solutions that contained neuroleptics for the animals that were placed in the chronic antipsychotic studies (see below). Table 1 provides the details for the all study cohorts, the numbers of animals tested per group, and the experiments conducted with each group. All procedures used during this study were reviewed and approved by the Medical College of Georgia Institutional Animal Care and Use Committee and are consistent with Association for Assessment and Accreditation of Laboratory Animal Care guidelines. Measures were taken to minimize pain or discomfort in accordance with the National Institutes of Health Guide for the Care and Use of Laboratory Animals (National Institutes of Health Publications 80-23) revised Significant efforts were also made to minimize the total number of animals used while maintaining statistically valid group numbers. Drug Dosing for Chronic Antipsychotic Experiments Oral antipsychotic dosing was based several factors: 1) for HAL, previous rodent studies in our laboratory in which time-dependent behavioral and neurochemical effects were detected and plasma drug levels were achieved that approximated those often associated with antipsychotic effects in humans (Terry et al., 2002, 2003, 2005a); and 2) for ZIP, previous studies using oral dosing in rodents in which notable behavioral effects were observed (Mansbach et al., 2001). Furthermore, for both HAL and ZIP, the doses selected (see below) would be expected to achieve comparable (and therapeutically) relevant D 2 receptor occupancy values in vivo (i.e., in the range 65 80%; see Kapur et al., 2003) based on the recent work of Barth et al. (2006). Rats were thus treated with 2.0 mg/kg/day HAL (Sigma- Aldrich, St. Louis, MO) or 12.0 mg/kg/day ZIP (Pfizer, Inc., New York, NY) orally for periods of 7, 14, 45, or 90 days. The antipsychotics were dissolved in 0.1 M acetic acid and subsequently diluted (1:100) with distilled, deionized water for daily drug administration in drinking water. Drug dosing was based on the average daily fluid consumption and the weight of the animals. Animals that were evaluated for residual neuroleptic-related behavioral effects were administered antipsychotics at the doses described above (or vehicle) for 90 days and then given a 1-week, drug-free washout period (i.e., returned to normal drinking water), behaviorally tested for 1 week, and then sacrificed for neurochemical studies (i.e., 2 weeks after the last drug exposure). Immunohistochemistry In the first series of immunohistochemical experiments, rats were administered the antipsychotics (or vehicle) as described above and sacrificed at different time points (7, 14, 45, or 90 days of treatment; Table 1) to determine whether there are time-dependent effects of antipsychotic treatment on NGF and ChAT. Nerve Growth Factor. Rats were deeply anesthetized with ketamine/xylazine and perfused with ice-cold 0.01 M phosphate-buffered saline (PBS) through the left cardiac ventricle to remove circu-

3 Neurobiological Comparisons of Haloperidol and Ziprasidone 711 TABLE 1 Study protocol details Study Title and Test Cohort Group n Treatment Days of Treatment Procedure mg/kg s Chronic antipsychotic: immunohistochemistry A 1 6 VEH 7 Sacrifice-ChAT staining 2 6 HAL Sacrifice-ChAT staining 3 6 ZIP Sacrifice-ChAT staining B 4 6 VEH 14 Sacrifice-ChAT staining 5 6 HAL Sacrifice-ChAT staining 6 6 ZIP Sacrifice-ChAT staining C 7 6 VEH 45 Sacrifice-ChAT staining 8 6 HAL Sacrifice-ChAT staining 9 6 ZIP Sacrifice-ChAT staining D 10 6 VEH 90 Sacrifice-ChAT staining 11 6 HAL Sacrifice-ChAT staining 12 6 ZIP Sacrifice-ChAT staining 13 6 VEH 7 Sacrifice-NGF staining E 14 6 HAL Sacrifice-NGF staining 15 6 ZIP Sacrifice-NGF staining 16 6 VEH 14 Sacrifice-NGF staining F 17 6 HAL Sacrifice-NGF staining 18 6 ZIP Sacrifice-NGF staining 19 6 VEH 45 Sacrifice-NGF staining G 20 6 HAL Sacrifice-NGF staining 21 6 ZIP Sacrifice-NGF staining H 22 6 VEH 90 Sacrifice-NGF staining 23 6 HAL Sacrifice-NGF staining 24 6 ZIP Sacrifice-NGF staining Behavioral task validations I 1 18 VEH-VEH 1 WM hidden platform 2 9 SCOP 0.1 -VEH 1 WM hidden platform 3 9 SCOP 0.1-DON WM hidden platform 4 9 SCOP 0.1-DON WM hidden platform J 5 15 VEH 1 Light/dark box 6 8 DIAZ Light/dark box 7 10 DIAZ Light/dark box 8 9 mcpp Light/dark box 9 8 mcpp Light/dark box K VEH-VEH 1 PPI VEH-APO 1 PPI HAL 0.01-APO PPI HAL 0.03-APO PPI HAL 0.10-APO PPI L VEH-VEH 1 PPI 16 8 VEH-MK PPI CLOZ 1.0-MK PPI CLOZ 2.0-MK PPI CLOZ 5.0-MK PPI M VEH-VEH 1 PPI SCOP 0.33-VEH 1 PPI 22 9 SCOP 0.33-DON PPI 23 8 SCOP0.33-DON PPI 24 8 SCOP 0.33-DON PPI Chronic antipsychotic: behavior and neurochemistry N 1 12 VEH 90 7-day washout WM (washout days 8 14, AM); light/dark box (day 10, PM); PPI (day 12, PM), sacrifice (day 14 of washout); ELISA/autoradiography O 2 12 HAL day washout WM (washout days 8 14, AM); light/dark box (day 10, PM); PPI (day 12, PM); sacrifice (day 14 of washout); ELISA/autoradiography P 3 12 ZIP day washout WM (washout days 8 14, AM); light/dark box (day 10, PM); PPI (day 12, PM); sacrifice (day 14 of washout); ELISA/autoradiography CLOZ, clozapine; DIAZ, diazepam; WM, water maze. lating blood elements. Brains were quickly removed and cryoprotected in embedding media. Coronal sections (20 m in thickness) were cut at interaural, 4.84 mm; bregma, 4.16 mm to obtain sections from hippocampus [dentate gyrus (DG); CA1 and CA3] (Paxinos and Watson, 1998) using a cryostat microtome (Leica CM 3050S; Leica Microsystems Inc., Chantilly, VA) at 20 2 C. Fresh frozen sections were fixed in ice-cold acetone for 30 min and airdried. Then, sections were rinsed in 0.01 M PBS containing Tween 20 (PBST). After blocking with 10% normal goat serum for 1 h, sections were washed and incubated overnight at 4 C with rabbit anti-mouse polyclonal NGF antibody (1:100) (Chemicon International, Temecula, CA). Endogenous peroxidase was blocked for 30 min with 0.1% H 2 O 2 and 100% methanol. Sections were then washed and incubated for 2 h with biotinylated anti-rabbit IgG antibody made in

4 712 Terry et al. goat (1:50) followed by incubation for 1 h with avidin-biotin-horseradish peroxidase complex. The avidin-hrp complex was then detected with 3 3 -diaminobenzidine tetrahydrochloride in the presence of 0.02% H 2 O 2 and nickel chloride (Vectastain kit; Vector Laboratories, Burlingame, CA). Choline Acetyltransferase. For ChAT immunohistochemistry, the method used has been described previously (Parikh et al., 2004a,b). In brief, rats were anesthetized and perfused with 100 ml of saline followed by 300 ml of ice-cold 4% paraformaldehyde in 0.1 M PBS. After perfusion, all brains were postfixed in paraformaldehyde for 2 h (with shaking) at 4 C followed by storage at 30% sucrose solution in 0.1 M PBS for 48 h. The tissues were embedded with OCT in liquid nitrogen and kept at 80 C until further use. A cryostat was used to cut 40- m coronal sections at specific anatomical landmarks: interaural, 4.84 mm; bregma, 4.16 mm to obtain sections from hippocampus (Paxinos and Watson, 1998). Cryoprotected fixed sections were washed three times in PBST, blocked with 10% normal horse serum for 1 h, and then incubated with 10 g/ml mouse monoclonal anti-chat antibody (Chemicon International) overnight at 4 C. The sections were washed three times with PBST and then incubated for 2 h with 1:20 diluted rat-adsorbed biotinylated horse anti-mouse IgG (Vector Laboratories) containing 1% horse serum. After washing, the sections were incubated with avidin-hrp for 1 h, and the avidin-hrp complex was subsequently detected with diaminobenzidine tetrahydrochloride. Quantitative Image Analysis. Photomicrographs from each treatment group were obtained with a Zeiss Axioplan-2 microscope equipped with a charge-coupled device camera, PC computer, and Zeiss KS-300 image analysis software by an experimenter blinded to the study code. The analysis for NGF was performed on live acquired images of dimensions m 2 in DG granule cell layer and m 2 each in CA1 and CA3 cell layer pyramidal neurons. For quantitation, densitometric assessments were made measuring the optical density (OD) of immunostained cells. The cells were considered positive if their OD values were higher than a defined threshold OD value above which only cell bodies and not processes were detectable. Three rectangles per section with dimensions m 2 for DG and m 2 for CA1 and CA3 region were delineated. NGF-immunoreactive neurons were identified in these regions, and staining intensity was expressed as mean OD obtained by averaging OD values of all stained profiles in analyzed field and subtracting the background OD of each section. OD range 0 to 2 was divided into 256 (0 255) digitized values. ChAT-immunoreactive nerve fibers in the hippocampus were analyzed as described previously (Parikh et al., 2004a,b). Three rectangles per section for DG, CA1, and CA3 subfields with similar dimensions as described above were selected for analysis. All the digitalized images of ChAT immunoreactive nerve fibers were converted to gray scale, and the brightness, contrast, and masking were adjusted to enhance the visibility of fibers (Photoshop 5.0; Adobe Systems, San Jose, CA). Quantitative data for ChAT-immunoreactive fibers are expressed as fiber pixel density. Behavioral Experiments In the behavioral studies, two series of experiments were conducted 1) behavioral task validation experiments and 2) comparisons of HAL and ZIP for residual effects on memory-related behavior performance after 90 days of treatment (i.e., a treatment period previously associated with HAL-induced memory impairments) beginning 1 week into a drug-free washout period. Behavioral Task Validation Experiments. In each of the validation experiments, identical conditions were used in each procedure as that used for the antipsychotic behavioral studies (see methodological details below). Thus, in spatial learning experiments, the water maze task used was assessed for its sensitivity to cholinergic antagonism (a central issue in this study) with a reference dose of scopolamine (0.1 mg/kg s.c. determined in preliminary experiments). Thereafter, two doses of the commonly used acetylcholinesterase inhibitor (AChEI) and cognitive-enhancing agent donepezil (Table 1) were evaluated for their ability to attenuate the impairing effects of scopolamine. Thereafter, the anxiety test used, the light-dark box test, was evaluated for its sensitivity to published reference doses (Table 1) of the anxiolytic agent diazepam and the anxiogenic agent meta-chlorophenylpiperazine (mcpp; see Chaouloff et al., 1997 and Bilkei-Gorzo et al., 1998, respectively). Finally, the prepulse inhibition (PPI) method used was evaluated for its sensitivity to known PPI impairing agents (and compounds known to attenuate the effects of such agents). Thus, dose-effect curves were established for the FGA haloperidol, the SGA clozapine, and the AChEI donepezil to reverse the impairing effects of reference doses of the dopamine agonist apomorphine, the N-methyl-D-aspartate antagonist MK801, and the muscarinic antagonist scopolamine on PPI, respectively. Drug doses (Table 1) were selected from previous work in our laboratory (Terry et al., 2005b) and other published PPI studies (Stanhope et al., 2001). Water Maze Testing. Testing apparatus. To determine the effects of the test drugs on spatial learning, water maze experiments were performed in a circular pool (180 cm in diameter, 76 cm in height) made of black plastic. For the task validation experiments, reference compounds (see above) were administered by subcutaneous injection acutely, and for the chronic (oral) neuroleptic studies, testing was begun on day 7 of a drug-free washout period (i.e., after the 90 days of oral drug dosing). The pool was filled to a depth of 35 cm with water (maintained at C). The pool was located in a large room with a number of extramaze visual cues, including geometric images (e.g., squares, triangles, and circles) hung on the wall, ambient lighting of approximately 25 to 30 lux (lumens per square meter), and black curtains, used to hide the experimenter (visually) and the resting test subjects. Swimming activity of each rat was monitored via a television camera mounted overhead, which relayed information, including latency to find the platform, total distance traveled, time, and distance spent in each quadrant, to a video tracking system (Actimetrics, Evanston, IL). Visible platform task. On the day before water maze hidden platform testing, a visible platform test was performed to ensure that the study subjects were visually capable of performing the task and that they demonstrated normal search/escape behaviors. To accomplish this task, a highly visible (white) cover fitted with a small white flag was attached to the platform (dimensions with cover attached cm), which raised the surface approximately 1.0 cm above the surface of the water. Each rat was gently lowered into the water in the quadrant diametrically opposite to the platform quadrant and given one or more trials with a 90-s time limit to locate and climb on to the platform. If unsuccessful after 90 s, it was physically placed on the platform for 30 s and then given a new trial. Once a rat was successful on its own accord, it was then given a series of four additional trials (with a 1.0-min intertrial interval) and the latency (in seconds) to locate the platform was recorded. The platform was moved on each trial to a different quadrant (the subject was always entered from the opposite quadrant) until the test was conducted once in all four quadrants. Hidden platform task. For these experiments, an invisible (black) cm square platform was submerged approximately 1.0 cm below the surface of the water and placed in the center of the northeast quadrant (which remained constant throughout hidden platform training). Each rat was given two trials per day for 6 consecutive days to locate and climb on to the hidden platform. A trial was initiated by placing the rat in the water directly facing the pool wall (i.e., nose approximately 2 cm from the wall) in one of the four quadrants. The daily order of entry into individual quadrants was pseudorandomized such that all four quadrants were used once every two training days. For each trial, the rat was allowed to swim a maximum of 90 s, to find the platform. When successful the rat was allowed a 30-s rest period on the platform. If unsuccessful within the allotted time period, the rat was given a score of 90 s and then physically placed on the platform and also allowed the 30-s rest

5 Neurobiological Comparisons of Haloperidol and Ziprasidone 713 period. In either case, the rat was given the next trial after an additional 1.5-min rest period (i.e., intertrial interval 2.0 min). Probe trials (transfer tests). Twenty-four hours following the last hidden platform trial, a probe trial was conducted in which the platform was removed from the pool to measure spatial bias for the previous platform location. This was accomplished by measuring the percentage of time spent in the previous target quadrant and the number of crossings over the previous platform location, and it provided a second estimate of the strength and accuracy of the memory of the previous platform location. Locomotor Activity and the Light/Dark Preference Test. To assess the effects test drugs on general locomotor activity as well as anxiety levels, a light/dark preference test (also referred to as light/ dark exploration or emergence neophobia test) was conducted. In this test, we were interested in determining whether the neuroleptics (i.e., day 10 of a drug-free washout) had significant motor effects that might have influenced performance in the memory-related tests. We were also interested to learn whether the neuroleptics (or reference compounds; see above) had any effects on anxiety levels (a factor that could at least theoretically influence performance in the water maze). The light/dark preference test is one of the most commonly used rodent models of anxiety (Holmes et al., 2001), and avoidance of the lighted portion of the chamber reflects elevated anxiety, whereas significantly reduced time spent in the dark area reflects an antianxiety effect of a test drug. MED Associates (St. Albans, VT) rat open field activity monitors ( cm) were used for these experiments. They were fitted with dark box inserts (which are opaque to visible light) to cover one-half the open field area, thus separating the apparatus into two zones of equal area (i.e., a brightly lit zone and a darkened zone). Desk lamps located above the activity monitors were used to provide an illumination level of approximately 1000 lux in the brightly lit zone, whereas the illumination level in the darkened zone was approximately 5 lux. The following parameters were recorded for the 5 min test session: horizontal activity (horizontal photobeam breaks or counts), number of stereotypy movements, vertical activity (vertical photobeam breaks) as well as the time spent in the light and dark zones of the apparatus. Thus, spontaneous locomotor activity, olfactory activity (rearing and sniffing movements), stereotypical movements, and emergence neophobia were assessed. Prepulse Inhibition Procedure. To assess the effects of the reference compounds (see above) and previous neuroleptic exposure (i.e., day 12 of a drug-free washout) on auditory gating (an important behavioral process that is often disrupted in schizophrenic patients), a PPI procedure was conducted as described previously (Terry et al., 2005a). Four startle chambers (San Diego Instruments, San Diego, CA) were used that consisted of a Plexiglas tube (8.2 cm in diameter, 25 cm in length) placed in a sound-attenuated chamber, in which the rats were individually placed. The tube is mounted on a plastic frame, under which a piezoelectric accelerometer is mounted, which records and transduces the motion of the tube. Two days before drug testing, the experimental subjects were each placed in one of the startle test chambers for a period of 10 min (without any startle stimuli) as an initial period of acclimation to the apparatus. One day before drug testing the animals were again placed in the test chamber and then exposed to 12 startle stimuli and to each prepulse level 3 times (see below). This procedure was done to reduce the highly variable responses to the initial exposures to the startle stimuli as well as to ensure that the prepulse stimuli (alone) had no significant effect on the startle response. On the day of drug testing, experimental subjects were transported to the startle chamber room and left undisturbed for at least 30 min. Afterward, the rats were placed in the chamber and then allowed to habituate for a period of 5 min, during which a 70-dB background white noise was present. After this period, the rats received 12 startle trials, 12 no-stimulus trials, and 12 trials of each of the prepulse/startle trials (see below) for a total of 60 trials. The intertrial interval ranged from 10 to 30 s, and the total session lasted approximately 25 to 30 min. The startle trials consisted of single 120-dB white noise bursts lasting 20 ms. The prepulse inhibition trials consisted of a prepulse (20-ms burst of white noise with intensities of 75, 80, or 85 db) followed, 100 ms later, by a startle stimulus (120-dB, 20-ms white noise). During the no-stimulus trial, no startle noise was presented, but the movement of the rat was recorded. This represented a control trial for detecting differences in overall activity. The 60 different trials were presented pseudorandomly, ensuring that each trial was presented 12 times and that no two consecutive trials were identical. The resulting movement of the rat in the startle chamber was measured during 100 ms after startle stimulus onset (sampling frequency 1 khz), rectified, amplified, and fed into a computer that calculated the maximal response over the 100-ms period. Basal startle amplitude was determined as the mean amplitude of the 12 startle trials. Prepulse inhibition was calculated according to the formula: [100 (startle amplitude on prepulse-pulse trials)/(startle amplitude on pulse alone trials) 100]. The mean level of PPI (i.e., averaged across the three prepulse intensities) was also analyzed. Enzyme-Linked Immunosorbent Assay Experiments After behavioral testing, some of the test subjects (Table 1) were anesthetized with KetaVed (ketamine hydrochloride injection; Vedco, Inc., St. Joseph, MO), intracardially perfused with PBS, ph 7.4, and then decapitated. Brains were quickly harvested, immediately frozen in dry ice-cooled 2-methylbutane (isopentane), and stored at 70 C until dissected for subsequent analyses. The basal forebrain, hippocampal formation, cortex, and prefrontal cortex were dissected and the homogenized in radioimmunoprecipitation assay buffer containing protease inhibitors and glycerol. Brain lysates were evaluated using ELISA methods to measure the relative levels of ChAT, vesicular acetylcholine transporter (VAChT), p75 neurotrophin receptor (p75 NTR ), TrkA (nerve growth factor receptor), phospho-trka (P-TrkA), and NGF. The brain dissections, preparation of brain lysates, protein assay, and ELISA methods (except NGF) were performed according to Gearhart et al. (2006), except that in the present study, different quantities of brain protein were analyzed by ELISA (see Table 2 for details). As an internal control for day-to-day variation in the ELISA methods, brain lysates (same amount of protein per well) from vehicle-, HAL-, and ZIP-treated rats were always assayed at the same time on the same ELISA plate. NGF was measured using the NGF Emax ImmunoAssay System (catalog no. G7631; Promega, Madison, WI) according to the kit instructions. The brain lysates were not acid-treated before the NGF ELISA. On the day of the NGF assay, the brain lysates were diluted in sample buffer (SB) as follows: basal forebrain lysate (30 l) SB (90 l), hippocampus lysate (30 l) SB (90 l), cortex lysate (60 l) SB (30 l), and prefrontal cortex lysate (60 l) SB (30 l). The diluted lysates were mixed thoroughly, and then 100 l of each diluted lysate was analyzed in the NGF ELISA. In addition, after preliminary experiments indicated that there were no significant differences in ELISA results between PBS-perfused animals and those sacrificed by decapitation (see below), some half-brains left from the autoradiography experiments were dissected and used in increase the sample size (n) in ELISA experiments. TABLE 2 Quantity of brain protein analyzed in each ELISA ELISA Method Basal Forebrain Micrograms Total Protein/ Microwell by Brain Region Hippocampus Cortex Prefrontal Cortex ChAT VAChT p75 NTR TrkA P-TrkA

6 714 Terry et al. Quantitative Receptor Autoradiography To assess the effects of prior chronic antipsychotic administration on cholinergic receptor densities, autoradiographic analyses of brain tissues harvested from rats previously exposed to HAL, ZIP, or vehicle were conducted with subtype-specific cholinergic radioligands to nicotinic acetylcholine receptors (nachrs) and muscarinic acetylcholine receptors (machrs), i.e., receptors that have been found to play important roles in learning and memory processes (van der Zee and Luiten, 1999; Rezvani and Levin, 2001). After behavioral testing, some of the test subjects (n 6 9) were immediately sacrificed by decapitation, the brains flash frozen. Using a Microm HM 505N cryostat ( 18 C; Richard Alan Scientific, Kalamazoo, MI), the left hemisphere of each brain was serially sectioned (16 m) up to the midline onto chrome alum/gelatin-coated slides. Low-affinity (homomeric 7 ) nachrs and high-affinity (heteromeric / subunit complexes) were labeled with 125 I- -bungarotoxin (BTX) and [ 3 H]epibatidine (EPB), respectively. The density of M 1 and M 2 machrs, i.e., the machrs expressed in highest quantities in mammalian brain (van der Zee and Luiten, 1999), were quantified using [ 3 H]pirenzipine (PRZ) and [ 3 H]AFDX384 (AFX), respectively. For each radioligand, the receptor subtype target, incubation time, concentration, and duration of film exposure are listed in Table 3. Please refer to previous publications for more detailed descriptions of the autoradiographic procedures (Hernandez and Terry, 2005; Terry et al., 2005a). Statistical Analyses All statistical analyses were performed using either SigmaStat 2.03 (SPSS Inc., Chicago, IL) or InStat, version 3.06 for Windows (GraphPad Software Inc., San Diego CA). Statistical significance was assessed using an alpha level of A one or two-way analysis of variance (ANOVA) (with repeated measures when indicated) was used for all treatment comparisons. In some cases, ranked data were used when the particular data set was non-normally distributed. For post hoc analysis, the Bonferroni method was used for multiple comparisons and Dunnett s test was used for cases when comparisons were made against vehicle control only. Raw ELISA data (optical density at 450 nm) were compared for all of the proteins with the exception of NGF in which picograms of nerve growth factor per milligram of protein were compared. For graphing purposes, the raw ELISA data were converted to percentage of the vehicle-treated group. Specifically, each OD (n 7 10 per HAL or ZIP group) from each ELISA (ChAT, VAChT, p75 NTR, TrkA, and P-TrkA) was divided by the mean OD for the vehicle-treated group (n 6 12) that was tested on the same ELISA plate. Similar calculations were used for the NGF results, except that the units were picograms of NGF per milligram of protein (rather than OD). The resulting quotients were multiplied by 100 to yield percentage of the vehicle-treated group, and then InStat was used to determine the mean S.E.M. For autoradiographic comparisons, a repeated measures two-factor ANOVA was used to examine differences in densitometry values between each treatment (HAL and ZIP) versus control within area of the brain. Animal was nested within the treatment and considered a random effect. Fixed effects were treatment and area of the brain. All two-factor interactions were included in the model. An level of 0.05 was used to examine post hoc differences on the adjusted least square means of the two-factor interaction between treatment from control and area of the brain. Results Immunohistochemistry NGF. Treatment comparisons (i.e., for effects on NGF immunoreactivity) made by measuring the mean optical density of immunostained cells are provided in Table 4. As indicated, NGF immunoreactivity was somewhat higher in the DG compared with the CA1 and CA3 regions of the hippocampus (which were similar). Interestingly, there was a notable increase in NGF immunoreactivity at 7 and 14 days of treatment with either HAL or ZIP in the DG, CA1, and CA3 areas of the hippocampus. After 45 days, however, animals treated with HAL had markedly reduced NGF immunoreactivity, whereas immunoreactivity in ZIP-treated subjects had returned to control levels. After 90 days of exposure to either HAL or ZIP, NGF levels were substantially lower than controls. ChAT. Varicose ChAT immunoreactive fibers were distributed in the granule cell layer of DG and in the pyramidal neurons of CA1 and CA3 subfields. The density of ChAT was TABLE 4 Drug effects on NGF immunoreactivity in the hippocampus Data are NGF (mean optical density S.E.M.) Treatment Region DG CA1 A3 7 Days VEH HAL ** ** ** ZIP ** ** ** 14 Days VEH HAL ** ** ** ZIP * ** ** 45 Days VEH HAL * ** *** ZIP Days VEH HAL *** *** *** ZIP *** *** *** * p 0.05; ** p 0.01; and *** p versus vehicle control, ANOVA (n 5 6/group). TABLE 3 Conditions for autoradiography on sagittal sections from rat brain Radioligands were from PerkinElmer Life and Analytical Sciences (Boston, MA). Film was BioMax MR-2 film (35 43 cm; no ; Eastman Kodak, Rochester, NY). Films were manually processed using Kodak GBX developer and fixer according to the manufacturer s protocol. Ligand Epibatidine -Bungarotoxin Pirenzepine AFDX-384 Receptor subtype target Nicotinic non- 7 Nicotinic 7 Muscarinic M 1 /M 4 Muscarinic M 2 Catalog no. NET-1102 NEX-1265 NET-780 NET-1041 Isotope 3 H 125 I 3 H 3 H Specific activity 55.5 Ci/mmol 17.0 Ci/ g 86 Ci/mmol 120 Ci/mmol Radioligand Incubation Concentration (nm) Preincubation time in buffer (min) None Radioligand incubation time (min) Film exposure time 13 wk 160 h 6 wk 16 wk

7 Neurobiological Comparisons of Haloperidol and Ziprasidone 715 TABLE 5 Drug effects on ChAT immunoreactivity in the hippocampus Data are ChAT (mean fiber pixel density S.E.M.). Treatment Region DG CA1 CA3 7 Days VEH HAL * ** ** ZIP * ** ** 14 Days VEH HAL * ** ** ZIP * * * 45 Days VEH HAL * ** ** ZIP Days VEH HAL *** *** *** ZIP *** *** *** * p 0.05; ** p 0.01; and *** p versus vehicle control, ANOVA (n 5 6/group). highest in the hippocampal CA3 pyramidal cell layer (Table 5). Representative images illustrating significant time-dependent, treatment-related effects on ChAT immunoreactivity (fiber pixel density) are provided in Fig. 1. The effects of the neuroleptics on ChAT immunoreactivity followed a similar pattern as the effects on NGF. Specifically, there was a significant increase in ChAT immunoreactivity at 7 and 14 days of treatment with either HAL or ZIP in the DG, CA1, and CA3 areas of the hippocampus. After 45 days, animals treated with HAL had markedly reduced ChAT immunoreactivity, whereas immunoreactivity in ZIP-treated subjects was similar to control levels. After 90 days of exposure to either HAL or ZIP, ChAT levels were substantially lower than controls. Behavioral Test Validation Experiments Water Maze Hidden Platform Test. Figure 2A illustrates the results of experiments in which a reference dose (0.1 mg/kg) of the muscarinic cholinergic receptor antagonist scopolamine was evaluated for its ability to impair spatial learning and for the effects of two doses of donepezil to reverse or attenuate these effects of scopolamine. The latency (number of seconds) of each experimental group to locate the hidden platform over 6 consecutive days of testing is depicted. There was a highly significant treatment effect (F 3,45 8.8; p 0.001), a significant day effect (F 5, ; p 0.001), without a significant treatment day interaction (F 225, ; p 0.8). Post hoc analyses indicated that performance was clearly impaired by scopolamine and that the higher (but not the lower) dose of donepezil attenuated this impairment. Specifically, the performance of controls (vehicle vehicle) and those administered scopolamine donepezil (2.0 mg/kg) was superior (p 0.05) to performance of the animals administered scopolamine vehicle on days 4, 5, and 6 and days 4 and 6, respectively. Light/Dark Box Experiments. Figure 2B illustrates the results of experiments in which reference doses of the anxiolytic agent diazepam and the anxiogenic agent mcpp were evaluated in the light/dark box test. There was a highly significant differences in response to the different drugs (F 4, ; p 0.001). Post hoc analyses indicated that 1) both doses of diazepam significantly (p 0.05) increased the amount of time spent in the illuminated arena (and that Fig. 1. Series of photomicrographs illustrating the time-dependent effects of the antipsychotics haloperidol and ziprasidone on ChAT immunoreactivity in the CA1 region of the hippocampus. HAL, haloperidol-treated; VEH, vehicle controls; and ZIP, ziprasidonetreated. Scale bar, approximately 100 m. n 6 rats/group.

8 716 Terry et al. Fig. 2. Behavioral task validation studies. A, water maze hidden platform studies in which a reference dose (0.1 mg/kg) of the muscarinic receptor antagonist scopolamine was evaluated for its ability to impair spatial learning, and two doses of the acetylcholinesterase inhibitor donepezil were evaluated for their ability to attenuate the effects of scopolamine. The latency (mean number of seconds S.E.M.) of each experimental group to locate a hidden platform over six consecutive days of testing is depicted., significantly different from scopolamine-vehicle treated animals (p 0.05). B, light/dark box experiments in which two doses of the anxiolytic agent diazepam and the anxiogenic agent mcpp were evaluated. Columns indicate the mean time (seconds) spent in the lighted zone ( S.E.M.)., significantly different from vehicle controls (p 0.05). #, dose-dependent effect of diazepam. C to E, results of experiments in which reference doses of known PPI-impairing agents (apomorphine, MK801, and scopolamine) and compounds known to attenuate the effects of these agents (haloperidol, clozapine, and donepezil, respectively) were evaluated. Columns represent the mean S.E.M. percentage of prepulse inhibition averaged across the three prepulse intensities (5, 10, and 15 db above background)., significantly different (p 0.05) from vehicle control response;, significantly different (p 0.05) from vehicle PPI antagonist-related response. APO, apomorphine; DON, donepezil; SCOP, scopolamine; VEH, vehicle. n 8 to 15 (see Table 1). there was a dose-related difference in response) compared with vehicle controls and 2) the higher (but not the lower) dose of mcpp was associated with a strong trend (p 0.06) toward decreased time spent in the illuminated arena. PPI Experiments. Figure 2, C to E, illustrates the results of experiments in which known PPI-impairing agents (and compounds known to attenuate the effects of such agents) were evaluated. The following results were observed (overall treatment effect, p in all three PPI validation studies): 1) apomorphine, MK801, and scopolamine at the doses evaluated (0.5, 0.1, and 0.33 mg/kg s.c., respectively) clearly diminished the effects of the prepulse stimuli on the acoustic startle response; 2) the FGA haloperidol (0.03, and 0.10 mg/kg i.p.) clearly attenuated the effects of apomorphine; 3) the SGA clozapine (5.0 mg/kg i.p.) clearly attenuated the effects of MK801; and 4) the AChEI donepezil (1.0 mg/kg s.c.) clearly attenuated the impairing effects of scopolamine (post hoc effects p 0.05 in all cases). Water Maze (Chronic Antipsychotic Studies) Visible Platform Test. Figure 3A illustrates the effect of the neuroleptics on the visible platform test (mean S.E.M. of four trials) in the water maze. This test was used as a method to ensure that the test subjects were not impaired visually and that they did not exhibit other (nonmnemonic) behaviors such as thigmotaxis that might have confounded the analyses. There were no significant treatment-related effects observed in this procedure (i.e., all p values were 0.05). Swim Speeds. Swim speeds were also analyzed (Fig. 3B) in an effort to further investigate treatment related differences in task performance. Average swim speeds ranged

9 Neurobiological Comparisons of Haloperidol and Ziprasidone 717 Fig. 3. Water maze tests beginning 7 days after the last day of a 90-day treatment period with either HAL or ZIP. A, visible platform test (mean S.E.M. of four trials). B, daily swim speeds (mean S.E.M. centimeter/second) during water maze hidden platform trials. C, hidden platform test (mean S.E.M.), two trials/day over 6 consecutive days of testing. Both HAL- and ZIPtreated animals performed less efficiently than controls., significantly different from vehicle controls (p 0.05). n 12 rats/group. between 15 and 20 cm/s across the groups for the 6 days of hidden platform testing. Statistical analyses revealed that there was not an overall treatment (group) effect (F 2,33 1.3; p 0.39) or day effect (F 5,10 1.4; p 0.25); however, there was a significant treatment day interaction (F 165, ; p 0.02). Post hoc analyses indicated that the only treatment-related difference in swim speeds occurred on day 2 of testing in which HAL-treated animals swam slightly (but significantly) faster than vehicle- and ZIP-treated animals. Hidden Platform Test. Figure 3C illustrates the efficiency of each experimental group to locate a hidden platform in a water maze task on six consecutive days of testing. For the latency comparisons, there was a highly significant treatment effect (F 2,33 8.0; p 0.001), a significant day effect (F 5, ; p 0.001), without a significant treatment day interaction (F 165, ; p 0.1). Post hoc analyses (for overall treatment effect across all days of testing) indicated that performance was superior in the vehicle-treated animals compared with both the HAL and ZIP animals (p and p 0.05, respectively). In the case of ZIP, all p values in the individual day comparisons were 0.05 (compared with vehicle controls), whereas in the case of HAL, there were several days where the performance was significantly different from controls (p 0.05; Fig. 2C). Probe Trials. Figure 4, A and B, illustrates the performance of probe trials by the various treatment groups. There were statistically significant (treatment-related) effects on performance as indicated by the percentage of the total time spent in the previous target quadrant [treatment effect (F 2,33 3.4; p 0.05)] and the number of crossing over the previous cm target area [treatment effect (F 2,33 7.5; p 0.01)]. Post hoc analysis indicated that performance was superior in the vehicle-treated animals compared with HALtreated animals in both measures (p and p 0.01, respectively). In the case of ZIP, there was a not a significant difference (compared with control), although there was a trend toward a performance decrement in the platform crossing analysis (p 0.1). Fig. 4. Water maze probe trials conducted 14 days after the last day of a 90-day treatment period with either HAL or ZIP. A, percentage of total time spent swimming in the previous target quadrant (mean S.E.M). B, platform area crossings (mean S.E.M.)., significantly different from vehicle controls (p 0.05). n 12 rats/group. Locomotor Activity and the Light/Dark Preference Test (Chronic Antipsychotic Studies) Figure 5, A to D, illustrates the effects of the drug treatments on horizontal and vertical locomotor activity, stereotypical movements as well as fear/anxiety-related behaviors (i.e., time spent in the lighted zone of the test apparatus). There were no significant treatment-related differences (p 0.05) in horizontal activity, vertical activity, or stereotypical movements. There were also no significant drug related effects on the light/dark preference test, although there was a strong trend toward a reduction in anxiety-related behaviors in the ZIP group (treatment effect: F 2,30 3.3; p 0.053). PPI Experiments (Chronic Antipsychotic Studies) The effects of 90 days of prior exposure to the neuroleptics on PPI testing assessed on day 12 of the drug-free washout are presented in Fig. 6, A to C. There was a highly significant (prepulse intensity-dependent) reduction in the startle response when the prepulse stimuli preceded the startle stimulus, prepulse level effect (F 2,4 41.1; p 0.001) (Fig. 5A). Post hoc analysis indicated that a graded

10 718 Terry et al. Fig. 5. Effects of prior chronic oral treatment with HAL or ZIP on locomotor activity and the light/dark box test (day 10 of a drug-free washout). A, vertical activity measured as the mean number of photobeam breaks/5 min). B, horizontal activity measured as the mean number of photobeam breaks/5 min). C, stereotypical movements (repetitive photobeam breaks/5 min). D, fear/anxiety-related behavior (emergence neophobia) measured as the time spent in a brightly lit zone of the activity monitor. Columns represent the mean S.E.M. n 12. Fig. 6. A, effects of prior chronic oral treatment with HAL or ZIP (i.e., testing on day 12 of a drug-free washout) on the percentage of prepulse inhibition in rats for three prepulse intensities (5, 10, and 15 db above background). B, drug effects on the mean startle amplitude to 120-dB, 20-ms noise burst. C, drug effects on the percentage of prepulse inhibition averaged across the three prepulse intensities (5, 10, and 15 db above background). Columns represent mean S.E.M. for each treatment (n 12). There were no significant treatment-related effects (i.e., all p values were 0.05). response to the increasing prepulse intensities was present (i.e., db) in all treatment groups; however, there were no significant differences in responses to the various drug treatments (F 2,27 0.9; p 0.44). Likewise, the treatment prepulse level interaction was not significant (F 54,89 0.9; p 0.49). Additional analyses revealed that the drugs also had no significant effects on the startle response (F 2,27 0.4; p 0.70) (Fig. 5B). Figure 5C depicts the overall effects of the treatments on PPI (i.e., averaged across prepulse intensity). ELISA Experiments Figure 7 summarizes ELISA results for ChAT, VAChT, p75 NTR, TrkA, phospho-trka, and NGF in memory-associated brain regions from rats treated with HAL (Fig. 7, A D) or ZIP (Fig. 7, E H). Each plot is presented in the same format. ELISA results from drug-treated rats are presented as a percentage of vehicle-treated rats; each column is labeled with the name of the protein measured (sample number in parentheses); the left two columns show levels of the cholinergic marker proteins ChAT and

11 Neurobiological Comparisons of Haloperidol and Ziprasidone 719 Fig. 7. ELISA results (expressed as percentage of vehicle-treated group) for memory-related brain regions from rats treated with haloperidol (A D) or ziprasidone (E H). Rats were euthanized 14 days after 90 days of antipsychotic treatment, and then the dissected brain regions basal forebrain (A and E), hippocampus (B and F), cortex (C and G), and prefrontal cortex (D and H) were processed for ELISA. Proteins detected by ELISA were ChAT, VAChT, p75 NTR, NGF, TrkA, and P-TrkA. For each column, # is the number of rats per group., p 0.05;, p 0.01;, p 0.001;, p , significantly different from vehicle control. VAChT; the middle three columns depict data for the NGF receptors (p75 NTR, TrkA, and phospho-trka); and the far right column represents the amount NGF protein. The horizontal dashed line is drawn at 100% of the vehicletreated group (i.e., columns near this line indicate similar protein levels between vehicle- and drug-treated groups). HAL-Treated Rats. HAL treatment did not change ChAT levels in any of the four brain regions tested; however, VAChT protein was significantly decreased in the hippocampus ( 25%; Fig. 7B) and prefrontal cortex ( 10%; Fig. 7D). HAL-treatment had modest effects on the levels of NGF-receptors (p75 NTR, TrkA, and phospho-trka), except for an 50% decrease in phospho-trka protein in the hippocampus (Fig. 7B). It is noteworthy that HAL-treated rats had significantly less NGF protein in the basal forebrain ( 25%; Fig. 7A), cortex ( 20%; Fig. 7C), and prefrontal cortex ( 20%; Fig. 7D). ZIP-Treated Rats. In contrast to HAL, ZIP treatment significantly decreased (by 15 25%) ChAT and VAChT in the hippocampus (Fig. 7F) and prefrontal cortex (Fig. 7H). ZIP treatment had little to no effect on the levels of NGF receptors (p75 NTR, TrkA, and phospho-trka) in the basal forebrain (Fig. 7E) and cortex (10% increase in TrkA; Fig. 7D). In the hippocampus from ZIP-treated rats (Fig. 7F), p75 NTR and TrkA were slightly decreased, whereas phospho-trka protein decreased by 35%. In the prefrontal cortex from ZIP-treated rats (Fig. 7H), p75 NTR and TrkA were reduced by 25 and 10%, respectively. Like HAL, ZIPtreated rats had significantly less NGF protein in the basal

12 720 Terry et al. TABLE 6 Nicotinic receptors: 7 ( 125 I-bungarotoxin) and 4 / 2 ( 3 H epibatidine) Amersham autoradiographic 125 Ior 3 H microscales were placed in each film cassette and then analyzed to generate standard curves (OD versus nanocuries of ligand per milligram of tissue equivalents). Binding values are expressed as nanocuries per milligram of tissue equivalents. Each value represents the mean S.E.M. of six to nine rats. 125 I-Bungarotoxin 3 H Epibatidine Brain Region Vehicle Haloperidol Ziprasidone Vehicle Haloperidol Ziprasidone Cerebral cortex Lamina I Lamina II Lamina III VI Lamina I V (medial) Lamina I V (lateral) Lamina VI (medial) Lamina VI (lateral) Entire cortex Entire cortex (medial) Entire cortex (lateral) Prefrontal Prefrontal (medial) Prefrontal (outer) Cingulate * * Entorhinal (lateral) Entorhinal (medial) Entorhinal (entire) Retrosplenial angular Hippocampal formation CA1 (lateral) CA1 (dorsal) CA1 (ventral) CA2 (dorsal) CA2 (ventral) CA2/C3 (medial) CA3 (dorsal) Dentate gyrus (dorsal) Dentate gyrus (lateral) Dentate gyrus (ventral) Polymorph layer of dentate gyrus (dorsal) Polymorph layer of dentate gyrus (lateral) Dentate gyrus (entire) Molecular layer of dentate gyrus Subicular complex Presubiculum Postsubiculum Subiculum Subiculum (medial) Subiculum (lateral) Thalamic nuclei Medial dorsal Antereoventral * Olfactory nuclei Accessory olfactory bulb Anterior olfactory nucleus Olfactory bulb Other nuclei Basal nucleus Lateral septal Triangular septal nucleus Posterior cortical amygdaloid nucleus Medial amygdala Basolateral amygdala (medial) Basolateral amygdala (lateral) Mammillary nuclei Mammillary peduncles Substantia innominata * indicates significantly different (p 0.05) from vehicle-associated value. forebrain ( 30%; Fig. 7E) and prefrontal cortex ( 35%; Fig. 7H). Autoradiographic Data Autoradiographic results are depicted in Tables 6 and 7. Representative autoradiograms are illustrated in Fig. 8. For each of the radioligands used in this study, the pattern of binding site distribution was similar to that observed in a previous study (Hernandez and Terry, 2005). Statistical analyses revealed that for each of the ligands there were highly significant regional binding differences (area effect p 0.001) as expected; however, there were no significant, overall treatment-related differences or treatment brain area interactions (i.e., all p values were 0.05). Post hoc analyses on individual brain areas did reveal a few select, treatment-related differences, however (see below).

13 Neurobiological Comparisons of Haloperidol and Ziprasidone 721 TABLE 7 Muscarinic receptors: M 2 receptor ( 3 H AFDX-384) and M 1 /M 4 receptor ( 3 H pirenzepine) Amersham autoradiographic 3 H microscales were placed in each film cassette and then analyzed to generate standard curves (OD versus nanocuries of ligand per milligram of tissue equivalents). Binding values are expressed as nanocuries per milligram of tissue equivalents. Each value represents the mean S.E.M. of eight to nine rats. 3 H AFDX H Pirenzepine Brain Region Vehicle Haloperidol Ziprasidone Vehicle Haloperidol Ziprasidone Cerebral cortex Lamina I Lamina I (medial) Lamina I (lateral) Lamina II (medial) Lamina II (lateral) Lamina VI Lamina I V Entire cortex Prefrontal Entorhinal Piriform Retrosplenial Hippocampal formation CA1 region (lateral) CA1 Region (dorsal) CA1 region (entire) CA2 region (entire) CA2/C3 region (lateral) CA2/C3 region (dorsal) CA2/C3 region (entire) CA3 region (entire) Dentate gyrus (dorsal) Dentate gyrus (lateral) Dentate gyrus (entire) Polymorph layer of dentate gyrus Thalamic nuclei Medial dorsal Antereoventral Olfactory nuclei Anterior olfactory nucleus Olfactory Bulb (external plexiform layer) Olfactory bulb (internal plexiform layer) Olfactory bulb Olfactory tubercle Other nuclei Amygdala Substantia innominata Medial septal Pontine * Subiculum Basal nucleus of stria terminalis Basal nucleus Nicotinic Receptor Expression. 125 I-BTX. Binding of 125 I-BTX was widely distributed across all regions of the brain, with the exception of the striatum and cerebellum (Table 6; Fig. 8). The highest 125 I-BTX binding densities were observed in the accessory olfactory bulb, supraoptic nuclei, mammillary nuclei, dorsal raphe, and medial vestibular nuclei. Moderate binding was observed in the superior colliculus, hippocampus, hypothalamus, and tegmental nuclei. Lower binding densities were observed in the cerebral cortex and amygdala. There were no significant differences in 125 I-BTX binding associated with the different antipsychotic treatments (all p values were 0.05 in post hoc analyses). [ 3 H]EPB. The highest [ 3 H]EPB binding densities were observed in the medial habenular nuclei, interpeduncular nuclei, and pineal gland (Table 6; Fig. 8). Moderate binding was observed in the anterior thalamus and subicular complex, whereas lower binding densities were observed in the cerebral cortex and individual cortical layers. Of the 19 areas measured, antipsychotic-treated animals exhibited a statistically significant difference from vehicle controls (in post hoc analyses) in two areas, the cingulate cortex and the anteroventral thalamic nucleus. In the cingulate cortex both HAL and ZIP were associated with a decrease in binding sites, whereas in the anteroventral thalamic nucleus binding was significantly increased by HAL (compared with vehicle controls). Muscarinic Receptor Expression. [ 3 H]AFX. The highest [ 3 H]AFX binding densities were observed in olfactory areas, the caudate putamen, and accumbens nuclei, whereas moderate binding was found in the cortex, basolateral amygdala, and hippocampal formation (Table 7; Fig. 8). Of the 24 areas measured, antipsychotic-treated animals exhibited a statistically significant difference from vehicle controls (in post hoc analyses) in only one area. Specifically, binding was higher in the HAL-treated rats in the pontine nuclei compared with vehicle-treated rats. [ 3 H]PRZ. [ 3 H]PRZ binding was widely distributed in the

14 722 Terry et al. Fig. 8. Representative autoradiograms illustrating nachr and machr subtypes in rats labeled by the following radioligands: nachrs; 125 I- -bungarotoxin ( 7 ) and [ 3 H]epibatidine (predominantly 4 2 ); and machrs, [ 3 H]pirenzipine (M 1 /M 4 ), and [ 3 H]AFDX384 (predominantly M 2 ). Experiments were conducted using 16- m sagittal sections of brains from adult male Wistar rats treated with antipsychotics or vehicle for 90 days followed by a 14-day drug-free washout period. AON, anterior olfactory nucleus; CA1, CA1 region of the hippocampus; Cg, cingulate cortex; CON, vehicle controls; HAL, haloperidol-treated; OB, olfactory bulbs; and ZIP, ziprasidone-treated. cortex and hippocampal formation and minimally represented in the thalamus, hypothalamus, and midbrain (Table 7; Fig. 8). The highest [ 3 H]PRZ binding densities were observed in the telencephalic regions such as CA1 region of the hippocampus, dentate gyrus, nucleus accumbens, basolateral amygdala, neocortex caudate putamen, and anterior olfactory nuclei. There were no significant differences in [ 3 H]PRZ binding associated with the different antipsychotic treatments (all p values were 0.05). Discussion In the initial phase of this study, we observed that during the early time points of treatment (i.e., 7 and 14 days), both HAL and ZIP were associated with marked increases in NGF and ChAT immunoreactivity in the DG, CA1, and CA3 regions of the hippocampus. Such increases in NGF protein in the hippocampus have been previously observed in association with 14 days of HAL treatment (Ozaki, 2000). After 45 days, however, a very different pattern was observed; NGF and ChAT levels had abated to control levels in the ZIPtreated animals and had dropped significantly below control in HAL-treated animals. Moreover, after 90 days, NGF and ChAT levels were substantially lower than controls in both antipsychotic groups. The basis for this time-dependent (biphasic), growth factor and cholinergic response to the neuroleptics in the hippocampus is unclear, since such observations have not been reported previously. The pattern could reflect some compensatory (but unsustainable) growth factor response to a neurotoxic effect of the antipsychotics, or alternatively, some time-dependent reaction to their inhibitory D 2 receptor effects on cholinergic neurons. Interestingly, observations of time-dependent (biphasic), cholinergic responses to FGAs in the striatum of animals (similar to our observations in the hippocampus) have been discussed as a potential mechanism of their adverse motor effects in humans. Namely, an increase in the activity of cholinergic interneurons in the striatum, in response to FGAs, initially seemed to parallel the extrapyramidal side effects in humans, whereas longer treatment periods were associated with decreases in cholinergic activity below baseline (i.e., effects that correspond with the emergence of tardive dyskinesia; Miller and Chouinard, 1993; Kelley and Roberts, 2004). This phenomenon may reflect the inhibitory D 2 receptor effects on cholinergic interneurons by FGAs, which results in excessive neuronal activity, intracellular accumulation of calcium, and subsequent cell damage. Since D 2 receptors are relatively sparse in the septohippocampal pathway, it is unclear whether an analogous process would occur here. However, dopamine regulation (via the D 1 receptor) of septohippocampal cholinergic activity has been described previously (Day and Fibiger, 1994), and both HAL and ZIP have significant antagonist activity at D 1 receptors (Miyamoto et al., 2005). Our detection of sustained (HAL- and ZIP-related) decreases in cholinergic markers in the cortex (described further below) may reflect the involvement of other dopamine-acetylcholine interactions. For example, it has been hypothesized that dopamine in the nucleus accumbens inhibits the activity of GABAergic projections to the basal forebrain, thereby modulating the excitability of cholinergic neurons that project to the cortex (Sarter and Bruno, 1999). Therefore, chronic exposure to drugs that antagonize mesolimbic dopamine receptors could indirectly lead to imbalances in cholinergic activity in basal forebrain neurons (and thus projection areas such as the cortex). In the second (behavioral testing) phase of the study, the task validation experiments indicated that 1) the water maze task used was sensitive to cholinergic manipulation (a central issue in this study), 2) reference anxiolytic and anxiogenic agents were active in the light/dark box procedure, and 3) the PPI task was sensitive to the effects of three known PPI-impairing agents and their antagonism by reference antipsychotic and cholinergic agents. In the chronic neuroleptic studies, rats previously treated with HAL were impaired in water maze hidden platform tests and probe trials (i.e., spatial learning/acquisition and retention). ZIP-treated animals were also impaired during task acquisition, although the magnitude of the deficits was lower than with HAL. The absence of HAL- or ZIP-related effects on swim speeds, visible platform tests, or in light/dark box/activity monitor experiments, argues against the premise that residual drug effects on locomotor activity, visual acuity, or anxiety levels underlie the observed deficits in water maze performance. The final behavior experiments were conducted to assess the